Mesenchymal hamartoma

Mesenchymal hamartoma is a 'tumour malformation' that develops in utero. It accounts for 8% of all liver tumours and pseudotumours from birth to 21 years of age, but during the first two years of life it represents 12% of all hepatic tumours and pseudotumours, and for 22% of the benign neoplasms {1839}. It usually manifests in the first two years of life and there is a slight male predominance. Lesions involve the right lobe in 75% of cases, the left lobe in 22% and both lobes in 3%.

Presentation is typically with abdominal swelling, but rapid accumulation of fluid in the tumour can cause sudden enlargement of the abdomen {1841}. Macrosco-pically, it is usually a single mass that can attain a large size (up to 30 cm or more). Mesenchymal hamartoma has an excellent prognosis after resection. The fate of untreated lesions is not known but there is no convincing evidence of malignant transformation.

Histopathology. This tumour-like lesion is composed of loose connective tissue and epithelial ductal elements in varying proportions. Grossly, the cut surfaces exhibit solid, pink-tan areas and cysts containing a clear fluid. Histologically, the connective tissue is typically loose and oede-matous with a matrix of acid mucopoly-

Table 8.05

Presentation of mesenchymal tumours of the liver. Mode of Presentation

Asymptomatic (incidental finding) Upper abdominal mass +/- hepatomegaly Sudden increase in size of tumour

Febrile illness with weight loss

Acute abdominal crisis from rupture

Budd-Chiari syndrome Congestive heart failure Cardiac tumour syndrome Consumption coagulopathy

Hypoglycaemia Portal hypertension

Liver failure

Obstructive jaundice Lung metastases

Examples

Any Any

Mesenchymal hamartoma, cavernous haemangioma Inflammatory pseudotumour, embryonal sarcoma, angiosarcoma Cavernous haemangioma, angiosarcoma, epithelioid haemangioendothelioma Epithelioid haemangioendothelioma Infantile haemangioendothelioma Embryonal sarcoma Cavernous haemangioma, infantile haemangioendothelioma Solitary fibrous tumour Epithelioid haemangioendothelioma, inflammatory pseudotumour Epithelioid haemangioendothelioma, angiosarcoma Inflammatory pseudotumour Epithelioid haemangioendothelioma, angiosarcoma

Fig. 8.62 Infantile hemangioendothelioma. A Red and brown tumour with focal hemorrhage. B Multiple brown cavitary lesions. C The tumour is well circumscribed but not encapsulated, and consists of small vessels. D Masson trichrome stain shows vessels lined by a single layer of plump endothelial cells surrounded by a scant fibrous stroma. Note the scattered bile ducts.

Fig. 8.62 Infantile hemangioendothelioma. A Red and brown tumour with focal hemorrhage. B Multiple brown cavitary lesions. C The tumour is well circumscribed but not encapsulated, and consists of small vessels. D Masson trichrome stain shows vessels lined by a single layer of plump endothelial cells surrounded by a scant fibrous stroma. Note the scattered bile ducts.

saccharide, or it is collagenous and arranged concentrically around the ducts. Fluid accumulation leads to separation of the fibres with formation of lym-phangioma-like areas and larger cavities. The epithelial component consists of bile ducts that may be tortuous and occasionally dilated. The ducts often are arranged in a ductal-plate-malformation pattern. Islets of liver cells without an aci-nar architecture may be present. Numerous arteries and veins are scattered throughout, as are foci of extra-medullary haematopoiesis.

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